TLV3702: Comparator used as Opamp

Hi Joseph,

An amplifier can be used a comparator, however a comparator can not be used as an op amp.

Could you explain what you are trying to achieve in your circuit design?

Regards,
Jonny

Joseph,

Please take a look at the TLV2402 - it is a nanopowered amplifier with a 16V supply:

http://www.ti.com/product/TLV2402

Regards,
Jonny

Hello Joseph,

Yes. You can make a comparator into a very POOR amplifier if needed. But usually a open-collector/drain output is used and not a push-pull.

See section 21 of Appnorte AN-74:

A Quad of Independently Func Comparators (Rev. A)

The output 'PWM's" to create the linear output votlage. The compensation and integration is created by the output capacitor.

The TLV3702 push-pull output would not work too well...you would need to add several extra components.

Why are you trying to create an amplifier? We do have a few "combo" amp and comparator devices, such as the LM392 or TLV2304.

Hi Jonny,

thank you very much for the alternative solution. I do not havo so much PC board space and I need a Q1 grade reference and amplifier above 5V supply with nanopower consumption. Usig a dual comp/opa package might be an attractive soulution. One opa used to build a band gap (not needed very accurate) the other one to use as comparator. the TLV2402 might be ok, however the response time a little bit long. I have to investigate whether it can be acctepted or not.

Regards,

Joseph

Hello Paul,

thank you very much for the remarks and the apponte! Yes, You have right: the comparator push-pull output optimized for high speed switching (between two logic states) similarly to standard CMOS logic families. Therefore, if a push-pull comparator (output) were operated in linear range, it might cause increased current consuption (my assumptution why you warned).

Unfortunately, Neither the TLV2304 nor the 3402 are not Q1 grade device :(  Becasue the '3402 could be used as comparator (open drain device).

Maybe the TLV2402-Q, however, it has quite long reponse time if used as comaprator.

Regards,

Joseph

Joseph,

What would be an appropriate response time for your application? We could loop in the op-amps group to the thread and they might be able to help you select a more appropriate part!

Regards,
Jonny

Hello Jonny,

sorry for the delay, I was on holiday.

The response time of the '2402 almost acceptable, however tr<=100us needed.

Originally, I choosed the '3702 device bacause 1 package can serve all function (1 opamp + 1 comp function).

Regards,

Joseph 

Joseph,

Looping in the AMPS team to this post to see if they can suggest you the right part for your application.

Regards,
Jonny

Joseph,

TLV27L2 does provide the correct output voltage and has no input current which make it a good comparator. However, there is an ICC penalty for output high in comparator mode. Normal ICC per channel was just over 5uA when used in a linear mode. In a comparator mode with input difference swept from -16V to +16V (supply is also 16V), supply current was less than 5uA when output and input are low and nearly 35uA when output and input are high. 

Hello Ron,

thank you vm for the detailed information / investigation referring to the special features of the 27L2!

It is very helpful for me: because in my application its output spends much more time on L level than H thus the power consumption more favourable.

Kind regards,

Joseph